The present invention relates generally to medical devices and methods for welding biological tissue. In particular, the invention relates to performing a vascular anastomosis and, more particularly, to preferred devices and methods for sealingly joining a graft vessel, such as a coronary bypass graft, to the side wall of a target vessel, such as the aorta or a coronary artery, in an anastomosis.
A wide variety of medical procedures involve creating an anastomosis to establish fluid communication between two tubular conduits or organs in a patient. Coronary artery bypass graft (CABG) surgery, for example, often involves creating an anastomosis between blood vessels or between a blood vessel and a vascular graft to create or restore a blood flow path to the heart muscles. Such CABG surgery is necessary to overcome coronary artery disease, wherein plaque build-up on the inner walls of the coronary arteries causes narrowing or complete closure of these arteries. This results in insufficient blood flow and deprives the heart muscle of oxygen and nutrients, leading to ischemia, possible myocardial infarction, and even death. CABG surgery may be performed via a traditional open-chest procedure or a closed-chest or port-access thoracoscopic procedure.
CABG surgery may require the creation of one or more anastomosis depending upon whether a xe2x80x9cfree graftxe2x80x9d or a xe2x80x9cpedicle graftxe2x80x9d is employed. A xe2x80x9cfree graftxe2x80x9d is a length of conduit having open proximal and distal ends. A proximal anastomosis is required to connect the proximal end of the graft to a source of blood (e.g. the aorta) and a distal anastomosis is required to connect the distal end of the graft to the target vessel (e.g. a coronary artery). Free grafts may be autologous, such as by harvesting a saphenous vein or other venous or arterial conduit from elsewhere in the body, or an artificial conduit, such as Dacron or Goretex tubing. A xe2x80x9cpedicle graftxe2x80x9d is the result of rerouting a less essential artery, such as the internal mammary artery, from it native location so that it may be connected to the coronary artery downstream of the blockage. The proximal end of the graft vessel remains attached in its native position and only one anastomosis is required to connect the distal end of the graft vessel to the target vessel. In either case, the anastomosis may be between the end of the graft and an aperture in the side wall of the source or target vessel (a so-called xe2x80x9cend-to-sidexe2x80x9d anastomosis) or the anastomosis may be between an aperture in the side wall of the graft and an aperture in the side wall of the source or target vessel (a so-called xe2x80x9cside-to-sidexe2x80x9d anastomosis).
Current methods available for creating an anastomosis include hand suturing the vessels together. Connection of interrupted vessels with stitches has inherent drawbacks. For example, it is difficult to perform and requires great skill and experience on the part of the surgeon due in large part to the extremely small scale of the vessels. Coronary arteries typically have a diameter in the range of between about 1 to 5 mm, and the graft vessels have a diameter on the order of about 1 to 4 mm for an arterial graft such as a mammary artery, or about 4 to 8 mm for a vein graft such as a saphenous vein. In closed-chest or port access procedures, the task of suturing is even more challenging due to the use of elongated instruments positioned through the access ports for approximating the tissues and for holding and manipulating the needles and sutures used to make the anastomoses. Other drawbacks of connection with stitches are the long duration of the operation, during which period in conventional open-heart CABG surgery the heart is arrested and the patient is maintained under cardioplegic arrest and cardiopulmonary bypass. Cardiopulmonary bypass has been shown to be the cause of many of the complications that have been reported in conventional CABG, such as stroke. The period of cardiopulmonary bypass should be minimized, if not avoided altogether, to reduce patient morbidity.
One approach to coronary artery bypass grafting that avoids cardiopulmonary bypass is performing the suturing procedure on a beating heart. At present, however, safe, reproducible, and precise anastomosis between a stenotic coronary artery and a bypass graft vessel presents numerous obstacles including continuous cardiac translational motion which makes meticulous microsurgical placement of graft sutures extremely difficult. The constant translational motion of the heart and bleeding from the opening in the coronary artery hinder precise suture placement in the often tiny coronary vessel.
The above mentioned drawbacks of hand suturing have led to the development of various approaches to stichless vascular anastomosis. One approach involves the use of rigid rings, such a described in Geotz et al., INTERANL MAMMARY-CORONARY ARTERY ANASTOMOSIS-A Nonsuture Method Employing Tantalum Rings, J. Thoracic and Cardiovasc. Surg. Vol. 41 No. 3, 1961, pp. 378-386. This anastomosis method uses polished siliconized tantalum rings that are circumferentially grooved. The free end of the internal mammary is passed through a ring chosen according to the size of the stenotic coronary artery. The free end of the mammary artery is everted over one end of the ring as a cuff and fixed with a silk ligature that is tied around the most proximal of the circular grooves in the ring. The cuffed internal mammary artery is inserted into an incision in the target coronary artery. The ring is fixed in place and sealingly joined to the target coronary artery by tying one or more sutures circumferentially around the target vessel and into one or more circular grooves in the ring. An intimal-to-intimal anastomosis results and dissection of blood between the coronary artery and the cuffed internal mammary artery is largely prevented.
Other ring-related anastomotic approaches include that disclosed in Carter et al., Direct Nonsuture Coronary Artery Anastomosis in the Dog, Annals of Surgery, Volume 148, No. 2, 1958, pp. 212-218, and U.S. Pat. No. 4,624,257 to Berggren et al. However, no permanently satisfactory results have been reported with the use of rigid rings. A rigid ring presents a foreign body of relatively heavy weight which does not heal well and produces pressure necrosis. Moreover, the use of rigid rings that completely encircle the graft vessel and the arteriotomy creates a severe xe2x80x9ccompliance mismatchxe2x80x9d relative to both the coronary artery and the graft vessel and the anastomosis site which could lead to thrombosis. That is, recent studies suggest that the anastomosis site should not be dramatically different in compliance relative to either the coronary artery or the vascular graft, which is the case when using rigid rings to sealingly join two vessels together.
Other attempts at stitchless anastomosis involve the use of stapling devices. For example, U.S. Pat. No. 4,350,160 discloses a vascular stapling device for creating an end-to-end anastomosis between the internal mammary artery (IMA) or a vein graft and one of the coronary arteries, primarily the left anterior descending coronary artery (LAD). However, this device can only perform end-to-end anastomoses such that the coronary artery must first be severed and dissected from the surrounding myocardium and the exposed end everted for attachment. This technique is limited to cases where the coronary artery is totally occluded and there is no loss of blood flow by completely severing the coronary artery downstream of the blockage to make the anastomosis. Consequently, this device is not applicable where the coronary artery is only partially occluded and is not at all applicable to making the proximal side-to-end anastomosis between a bypass graft and the aorta.
U.S. Pat. No. 5,234,447 discloses a vascular stapling device for end-to-side vascular anastomoses. A ring-shaped staple is provided having legs extending from the proximal and distal ends of the ring for joining two blood vessels together in an end-to-side anastomosis. However, this device does not provide a complete system for quickly and automatically performing an anastomosis. Rather, it involves a great deal of manual manipulation of the staple, using hand operated tools to individually deform the distal lines of the staple after the graft has been attached and before it is inserted into the opening made in the aortic wall. One of the more difficult maneuvers in applying the staple involves carefully everting the graft vessel over the sharpened ends of the staple legs, then piercing the everted edge of the vessel with the staple legs. Experimental attempts to apply this technique have proven to be very problematic because of difficulty in manipulating the graft vessel and the potential for damage to the graft vessel wall. For speed, reliability and convenience, it is preferable to avoid the need for complex maneuvers while performing the anastomosis. Further bending operations must then be performed on the staple legs. Once the distal lines of the staple have been deformed, it may be difficult to insert the staple through the aortotomy opening.
Another disadvantage of the device of the ""447 patent is that the distal lines of the staple pierce the wall of the graft vessel at the point where it is everted over the staples. Piercing the wall of the graft vessel potentially invites leaking of the anastomosis and may compromise the structural integrity of the graft vessel wall, serving as a locus for a dissection or even a tear which could lead to catastrophic failure. Because the staple legs only apply pressure to the anastomosis at selected points, there is a potential for thrombosis. There is also the potential that exposure of the medial layers of the graft vessel where the staple pierces the wall could be a site for the onset of intimal hyperplasia, which would compromise the long-term patency of the graft. Because of these potential drawbacks, it is desirable to make the attachment to the graft vessel as atraumatic to the vessel wall as possible and to eliminate as much as possible the exposure of any foreign materials or any vessel layers other than a smooth uninterrupted intimal layer within the anastomosis site or within the graft vessel lumen.
Still other anastomotic approaches involve the use of anastomotic fittings for joining blood vessels together. U.S. Pat. No. 4,366,819, for example, discloses a vascular anastomotic fitting device for end-to-side vascular anastomoses. This device is a four-part anastomotic fitting having a tubular member over which the graft vessel is everted, a ring flange which engages the aortic wall from within the aortic lumen, and a fixation ring and a locking ring which engage the exterior of the aortic wall. Another similar device is described in U.S. Pat. No. 4,368,736. This device is a tubular fitting with a flanged distal end that fastens to the aortic wall with an attachment ring, and a proximal end with a graft fixation collar for attaching to the graft vessel. These devices have a number of drawbacks that the present invention seeks to overcome. Firstly, the anastomotic fittings described expose the foreign material of the anastomotic device to the blood flow path within the arteries. This is undesirable because foreign materials within the blood flow path can have a tendency to cause hemolysis, platelet deposition and thrombosis. Immune responses to foreign material, such as rejection of the foreign material or auto-immune responses triggered by the presence of foreign material, tend to be stronger when the material is exposed to the bloodstream. As such, it is preferable that as much as possible of the interior surfaces of an anastomotic fitting that will be exposed to the blood flow path be covered with vascular tissue, either from the target vessel or from the graft vessel, so that a smooth, continuous, hemocompatible endothelial layer will be presented to the bloodstream. The anastomotic fitting of the ""819 patent also has the potential drawback that the spikes that hold the graft vessel onto the anastomotic fitting are very close to the blood flow path, potentially causing trauma to the blood vessel that could lead to leaks in the anastomosis or compromise of the mechanical integrity of the vessels. Consequently, it is desirable to provide an anastomosis fitting that is atraumatic to the graft vessel as possible. Any sharp features such as attachment spikes should be placed as far away from the blood flow path and the anastomosis site as possible so that there is no compromise of the anastomosis seal or the structural integrity of the vessels.
Another device, the 3M-Unilink device for end-to-end anastomosis (U.S. Pat. Nos. 4,624,257; 4,917,090; 4,917,091) is designed for use in microsurgery, such as for reattaching vessels severed in accidents. This device provides an anastomosis clamp that has two eversion rings which are locked together by a series of impaling spikes on their opposing faces. However, this device is awkward for use in end-to-side anastomosis and tends to deform the target vessel; therefore it is not currently used in CABG surgery. Due to the delicate process needed to insert the vessels into the device, it would also be unsuitable for port-access surgery.
In order to solve these and other problems, it is desirable to provide an anastomosis device capable of performing end-to-side and/or side-to-side anastomosis between blood vessels or other hollow organs and vessels. It is also desirable to provide an anastomosis device which minimizes the amount of foreign materials exposed to the blood flow path within the blood vessels and which avoids leakage problems, and which promotes rapid endothelialization and healing. Further, it would be desirable to provide such a device which could be used in port-access CABG surgery. Whether it is used with open-chest or closed-chest surgical techniques, it is also desirable that the invention provide a complete system for quickly and automatically performing an anastomosis with a minimal amount of manual manipulation.
The present invention involves an anastomosis system and method suitable, by way of example, for use in establishing fluid communication between a graft conduit and a blood vessel in coronary artery bypass graft (CABG) surgery. The anastomosis system of the present invention establishes such fluid communication by employing tissue fusion technology to effectively fuses the graft conduit to the blood vessel, thereby eliminating the need for connectors or similar prior art devices that remain implanted following the anastomosis procedure. The system may be used to create side-to-side and/or end-to-side anastomosis connections. It may also be employed in either open-chest or closed chest procedures.